I would definitely be interested in answering any questions you have on how to use GIMP.
Here are some tips:
1. I use "LAYERS" and once you see how easy it is to use, you will too! If it is not already up, type alt/"L" (altogether) and a simplified
"LAYER" box will appear. Then you can click on a new layer to work on and go back and forth to different layers. (To add a new layer, click
on the little box at the bottom left.) This makes is really easy to make changes without having to erase a lot. You can then MERGE them
together (look under Layers), or just save as a .png file and it will merge for you. You can save the whole file with layers intact as a .xcf file.
When you re-open the file, the layers will all still be there.
2. I am also a big fan of the "By-Color-Select" tool (the "red-green-blue boxes in a row" tool - you can use it to select a specific color and it will
delete all of that color anywhere in the picture, so that you end up with a transparent background),
3. "Hue Saturation" (look under "colors" at the top of the window you are working on) - change the colors you have used to find other color-ways
or fine-tune the ones you have.
4. "Fuzzy select" (same as color selector, but will only highlight the color in the area you are working on).
5. "FILTERS" - Gaussian Blur - helps blend areas together (free select around the area and use GaussBlur at 1 or 2)
6. "Light & Shadow": Drop Shadow. Play around with the numbers and see the cool effects that the drop shadow gives you.
5. "Bucket fill" to fill in any area already blocked by lines, or that you have surrounded with the "Free Select".
6. Another fun tool to use is the CLONE tool - it will copy any area on the picture and reproduce it where you want it. (A good tool for fixing
damaged areas of a scan, by the way). Select the tool, then click where you want to "clone" holding down the control key, and then draw!
7. One of the best things you can do for your sanity is to use the keyboard shortcuts! If you click on "EDIT" and then go to "KEYBOARD
SHORTCUTS" a window will open with all of the tools etc, with keyboard strokes for each. You can turn on the ones that you use often
and customize them to keys that make sense to you. For example, I use "H" for Hue Saturation, "S" for "Scale" (change size of file"),
"E" for Erasure, "R" for rectangle select, "F" for "Free select, etc.
8. Oh and of course there is always "Copy and Paste": "c" for cut and "v" for paste. You can surround what you want to "cut" with the rectangle,
circle, or free "select" tools.
Hope that helps a bit!